Various types of medical electrical leads for use in cardiac rhythm management (CRM) and neurostimulation systems are known. For CRM systems, such leads are typically extended intravascularly to an implantation location within or on a patient's heart, and thereafter coupled to a pulse generator or other implantable device for sensing cardiac electrical activity, delivering therapeutic stimuli, and the like. The leads frequently include features to facilitate securing the lead to heart tissue to maintain the lead at its desired implantation site. Exemplary leads can include a helical fixation member that can be extended from the distal end of the lead and screwed into the cardiac tissue to fixate the lead in place.